Another 10K to 20K of expected life from the two older tires seems like a fairly significant number of miles to just "throw away" in the interest of getting more miles out of your tires. Sounds counter-productive to me.

I'm more concerned about any effect on the transfer case due to different diameter tires on the front and back axles. I don't want to try to save a little money today but end up spending more tomorrow.

The real catch is that if you want to switch to a new brand (which I wouldn't recommend doing unless you replace all four) is that you'll face the same dilemma when the two old tires are finally used up but the two new ones you buy now won't be due for replacement yet.

So if you do want to try a different brand, you're going to have to toss out at least a pair of perfectly good tires to do so. It's either now or later.

Part of the decision is due to the price of the tires. The Michelins are $189 per tire while the General tires are on sale for $110 (regularly $147). Since the blown tire is 100% covered under warranty, it'll cost me $110 (plus installation and other fees) for a pair of Generals or the cost of four Michelins minus credit for old General tire.